It's what me and my girlfriend do on her periods, most of the time. She likes it, and she hasn't had any problems yet. though I don't typically finger her when she's. Jul 19, - If you feel butt pain during your period, you're not alone. Here's why you might hurt down there that time of the month, and what you can do about it. Anal pain could also potentially point toward endometriosis, says ob/gyn.